If you don't read Daring Fireball already, you may consider this link also a recommendation to do so. In fact, I recommend becoming a member, and after you read John Gruber's comparison of the Firefox 3 and Safari 3 browsers, you'll know why.
John does an excellent job reviewing these two applications based on a number of factors including interface, design, feature-sets, and how well each fits into the Operating System.
"I love Firefox’s auto-restoration of tabs and windows. Quit Firefox, relaunch it, and your previously-open tabs and windows are restored. Safari 3 has this feature, but makes you do it manually via the “Reopen All Windows From Last Session” command in the History menu. I’m sure most Safari users have no idea this feature even exists. At least as a preference, Safari should offer the ability to do this automatically."
He's right. I never knew that feature was even there. It is little tidbits like this, and John's superb writing, that have made me never regret my membership fee to Daring Fireball.